Development server and hot reload in NextJS - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What happens when you save a file in a Next.js project running the development server?

You have a Next.js app running with npm run dev. You edit a component file and save it. What is the expected behavior?

A The development server stops and you must restart it manually to see changes.

B The browser automatically reloads the page showing the updated component without a full page refresh.

C Nothing happens until you refresh the browser manually.

D The app crashes and shows an error in the terminal.

💡 Hint

Think about how hot reload improves developer experience by updating the UI instantly.

Next.js development server supports hot reload, which updates the changed components in the browser automatically without a full page reload.

🔧 Debug

intermediate

Why might hot reload not update your component after saving changes?

You saved changes in a Next.js component, but the browser does not update automatically. What is a likely cause?

A You edited a file outside the <code>pages</code> or <code>app</code> directory and did not export the component properly.

B Your browser cache is disabled, preventing updates.

C You forgot to restart the development server after every save.

D Hot reload only works in production builds.

💡 Hint

Consider how Next.js detects changes and which files it watches.

Next.js watches files in pages and app directories. Editing files outside or missing exports can prevent hot reload from detecting changes.

📝 Syntax

advanced

What is the correct command to start the Next.js development server with hot reload enabled?

Choose the command that starts the Next.js development server with hot reload.

A next run

B next build

C next start

D next dev

💡 Hint

Think about which command runs the server in development mode.

next dev starts the development server with hot reload enabled. next start runs the production build.

❓ state_output

advanced

What will be the console output after saving this Next.js component file during development?

Given this component code, what will the terminal show after you save changes?

NextJS

export default function Hello() {
  return <h1>Hello, world!</h1>;
}

A Error: Unexpected token in JSX

B No output, the server crashes silently

C Compiled successfully. Ready on http://localhost:3000

D Warning: Component not exported

💡 Hint

Consider what happens when a valid component is saved in development mode.

Next.js recompiles the code and shows a success message with the local URL when the component is valid.

🧠 Conceptual

expert

Why does Next.js use hot reload instead of a full page reload during development?

Choose the best explanation for why Next.js prefers hot reload over full page reload when you save changes.

A Hot reload preserves the app state and updates only changed components, speeding up development.

B Full page reload is not possible in Next.js due to routing restrictions.

C Hot reload disables browser caching to improve performance.

D Full page reload causes the development server to restart.

💡 Hint

Think about how developers want to keep their app state while editing.

Hot reload updates only the changed parts without losing the app state, making development faster and smoother.